diff --git a/vars/default.nix b/vars/default.nix
index a4acd7f6..03faee7b 100644
--- a/vars/default.nix
+++ b/vars/default.nix
@@ -4,6 +4,7 @@
   useremail = "xiaoyin_c@qq.com";
   networking = import ./networking.nix {inherit lib;};
   # generated by `mkpasswd -m scrypt --rounds=11`
+  # https://man.archlinux.org/man/crypt.5.en
   initialHashedPassword = "$7$CU..../....KDvTIXqLTXpmCaoUy2yC9.$145eM358b7Q0sRXgEBvxctd5EAuEEdao57LmZjc05D.";
   # Public Keys that can be used to login to all my PCs, Macbooks, and servers.
   #